Field of the Invention
The present invention relates to a flat panel display including a thin film type backlight unit and method for manufacturing the same. More particularly, the present invention relates to a flat panel display including an ultrathin film type and high efficiency backlight unit using a holography technology.
Discussion of the Related Art
Nowadays, due to the characteristics of lightweight, slim thickness, low consumption electric power, liquid crystal display devices (LCDs) are widely applied to various electronic devices. LCDs are applied to portable computers such as notebook PCs, office automation devices, audio/video devices, advertising display devices for indoor or outdoor uses, and so on. Transmissive type LCDs, which are the most widely used, represent images by modulating the luminescence of the light incident from the backlight unit by controlling the electric field applied to the liquid crystal layer.
Typically, there are two types of backlight units: direct type and edge type. The direct type backlight unit has a structure in which a plurality of optical sheets and a diffusion plate are stacked under the liquid crystal panel and a plurality of light sources are disposed under the diffusion plate.
FIG. 1 is a cross-sectional view illustrating a structure of an LCD having a direct type backlight unit including an array of light emitting diodes (LED) as a light source according to the related art.
The direct type backlight unit DBLU includes a light source disposed under a liquid crystal panel LCDP and provides backlight directly to the liquid crystal panel LCDP. The light source may be a thin fluorescent lamp. Alternatively, as shown in FIG. 1, the light source may be an LED array LEDAR having a lower power consumption and enhanced luminescence.
The LED array LEDAR is disposed in a matrix configuration on the bottom surface of the case CASE. The case CASE may be installed at the cover bottom CB. In some cases, the case CASE may be omitted, and the LED array LEDAR may be disposed at the cover bottom CB directly. On the LED array LEDAR, a diffusion plate DIFF is disposed. The diffusion plate DIFF diffuses the backlight from the LED array LEDAR to provide evenly scattered backlight over the light incident surface of the liquid crystal panel LCDP. Between the diffusion plate DIFF and the liquid crystal panel LCDP, a plurality of optical sheets OPT may be disposed. The optical sheets OPT include one or more prism sheets, one or more diffusion sheets, and/or a dual brightness enhancement film (or DBEF). The prism sheets converse the scattered and/or diffused backlight by the diffusion plate DIFF to the liquid crystal panel LCDP for enhancing the brightness of the backlight. The diffusion sheets diffuse again the conversed backlight by the prism sheets over the liquid crystal panel LCDP to achieve evenly distributed luminescence.
A guide panel GP wraps and/or surrounds the side surfaces of the liquid crystal panel LCDP and the direct type backlight unit DBLU and supports the liquid crystal panel LCDP by inserting between the liquid crystal panel LCDP and the optical sheets OPT. The cover bottom CB wraps and/or surrounds the case CASE and the bottom surface of the direct type backlight unit. On the bottom surface of the case CASE having the LED array LEDAR, a reflective sheet REF is disposed to reflect the backlight leaked from the diffusion plate DIFF and/or the optical sheets OPT to the liquid crystal panel LCDP. The top case TP surrounds the upper edge of the liquid crystal panel LCDP and the side surface of the guide panel GP.
Meanwhile, the edge type backlight unit may have thinner thickness than the direct type backlight unit. Currently, LCDs have an LED light source rather than a fluorescent lamp. Especially, due to easy installation of the light source, the edge type backlight unit, in which LED light sources are disposed at the side surface of the liquid crystal panel, is more widely applied.
Hereinafter, the edge type backlight unit will be described in detail with reference FIG. 2.
FIG. 2 is a cross-sectional view illustrating a structure of an LCD having an edge type backlight unit including an array of light emitting diodes as a light source according to the related art.
Referring to FIG. 2, the edge type backlight unit comprises a cover bottom CB, a light guide LG disposed at a bottom surface of the cover bottom CB, and a light source disposed between the side surface of the light guide LG and the cover bottom CB and providing backlight to the side surface of the light guide LG. The light source may be a thin fluorescent lamp. Alternatively, as shown in FIG. 1, the light source may be the LED array LEDAR having a lower power consumption and enhanced luminescence. The light source may be disposed at the side surface of the light guide LG using an installing means like housing. The light guide LG receives the backlight from the LED array LEDAR and refracts the direction of the backlight as being perpendicular to the light incident surface of the liquid crystal panel LCDP. Between the light guide LG and the liquid crystal panel LCDP, a plurality of optical sheets OPT are disposed. The optical sheets OPT include one or more prism sheets, and one or more diffusion sheets for scattering and/or diffusing the backlight from the light guide LG. To enhance the brightness and/or luminescence, the optical sheets OPT may further include a dual brightness enhancement film (or DBEF).
The guide panel GP wraps and/or surrounds the side surfaces of the liquid crystal panel LCDP and the edge type backlight unit, and supports the liquid crystal panel LCDP by inserting between the liquid crystal panel LCDP and the optical sheets OPT. Between the cover bottom CB and the light guide LG, a reflective sheet REF is disposed to reflect the backlight leaked from the diffusion plate DIFF and/or the optical sheets OPT to the liquid crystal panel LCDP. The top case TP surrounds the upper edge of the liquid crystal panel LCDP and the side surface of the guide panel GP.
LCDs, which are not a self-luminance display, typically have a backlight unit. A backlight unit can be configured to provide backlight evenly distributed over the whole surface of the liquid crystal panel. Therefore, various optical devices and/or means are used to transform light from a point light source or line light source to light from a plane light source. Further, considering the optical characteristics and structures of these optical devices and/or means, the backlight unit would have some thickness. Even though flat type displays including LCDs are remarkably slimed than the conventional displays like cathode ray tubes (CRT), a new backlight unit suitable for a display device with slim profile and lower power consumption is in demand.